1. Field of the Invention
The present invention relates to the field of electronic circuits. More specifically, the invention relates to circuits which reduce the effect of inrush currents.
2. Description of Related Art
When an electric motor is first activated, the drive circuit supplying power thereto often exhibits initial currents, called inrush currents, that can be orders of magnitude greater than the circuit's steady state currents. Even though the inrush currents account for only a very small percentage of a circuit's operating time, circuit designers often use components designed for applications at or even above the inrush currents to ensure the circuit will not fail during activation.
However, it is often advantageous in certain applications to design circuits to use lower power components. For example, board-mounted transformers provide designers the ability to reduce circuit complexity, avoid/meet governmental regulations, more easily dissipate heat, and significantly reduce costs and complexities. The drawback to board-mounted transformers, however, is that they can be rated to power specifications lower than specific applications require.
Accordingly, circuit designers often must choose between using circuit components that are not rated for certain inrush levels, thereby potentially underpowering and/or overloading the desired circuit, or using circuit components that add significant cost and complexity to a particular design. In some applications, such as applications having significantly limited power and/or limited cost margins, use of the costly and complex circuit components can defeat the application at the design stage. For example, in the design of exercise equipment, certain desirable features may have significant cost and design limitations, such as, for example, personal cooling systems including air flow mechanisms like fans. When the design of such mechanisms use components rated to account for inrush currents, the added cost and complexity can dictate their removal from the design.